Problem: Solve for $x$ : $5x^2 - 30x + 45 = 0$
Dividing both sides by $5$ gives: $ x^2 {-6}x + {9} = 0 $ The coefficient on the $x$ term is $-6$ and the constant term is $9$ , so we need to find two numbers that add up to $-6$ and multiply to $9$ The number $-3$ used twice satisfies both conditions: $ {-3} + {-3} = {-6} $ $ {-3} \times {-3} = {9} $ So $(x - {3})^2 = 0$ $x - 3 = 0$ Thus, $x = 3$ is the solution.